1. Field of the Invention
The present invention relates to a driving method and a driving apparatus, and in particular to a method and an apparatus for driving multi-segment display device.
2. Description of Related Art
To drive multi-segment display devices used to illustrate characters (e.g. numeric or alphabetical), a clock signal having continuous square wave and a control continuous wave as an input signal is conventionally used to determine whether a “ON” or “OFF” mode is used. With a driving circuit, the input signal is converted into a continuous square wave having two polarities. Amplitudes of the continuous square wave are used to determine whether the “ON” or “OFF” modes of corresponding pixels are used. Because many display media well known in the art such as liquid crystal (LC) display medium or non-LC display medium have different characteristics, it therefore arises an issue to drive the pixels into “ON” mode for multi-segment display devices accompanying with also driving the corresponding electrically wires into “ON” mode by the conventional segment driving.
In addition, when the multi-segment display devices are assembled, segment electrodes corresponding to the segments of upper substrates and lower substrates need to be aligned accurately. This results in higher costs and low production yield. To overcome the above-mentioned disadvantages, it is usually improved to avoid the driving electrical wires in the process by, for instance, increasing the light-absorbing layer upon the electrical wires or avoiding the electrical wires with respect to different display media such as electrochromic display (ECD) which disposes the display medium in the right positions to avoid the electrical wires. However, it is not a direct means to solve the electrical wires to be mistakenly driven into the “ON” mode.
FIG. 1A is a conventional driving circuit for a display device. Referring to FIG. 1, each pixel of the display device corresponds to a set of input signals and a conversion circuit 16. The conventional driving circuit includes a control input terminal 12 and an input signal terminal 10. A clock signal is supplied to the control input terminal 12 of the conventional driving circuit, and the frequency of the clock signal is the AC signal having two polarities supplied to corresponding pixel of the display device. A logic control signal is supplied to the input signal terminal 16 and used to switch between the “ON” or “OFF” modes of the corresponding pixels. Also, both the control input terminal 12 and the input signal terminal 16 are coupled to an exclusive OR (XOR) gate 14. Then, the control input terminal 12 and the input signal terminal 16 are connected to an amplifier or a signal scaler so that logic output levels are converted to a plurality of voltages. The voltages include a segment voltage 18 and a common voltage 20, and are used to drive display medium 22 of the display devices.
FIG. 1B shows segment driving waveforms of the segment voltages of the conventional driving circuit. Referring to FIG. 1B, a waveform of signal supplied to the input signal terminal 10 is indicated by reference numeral 100, and a waveform of signal supplied to the control input terminal 12 is indicated by reference numeral 102. A waveform of signal having the common voltage 20 is indicated by reference numeral 104. A waveform of signal having the segment voltage 18 is indicated by reference numeral 106. A waveform of a signal having a voltage drop of the common voltage 20 and the segment voltage 18 is indicated by reference numeral 108. The signal having the waveform 108 has a voltage to activate the display medium. The waveform of the signal supplied to the segment electrodes and the common electrodes has amplitudes of F, and the signal has one polarity. However, the segment electrodes and the common electrodes are likely positioned opposite to the backgrounds of display device. Electrical fields generated by the signals having the waveform 108 have impact on the modes of display medium. Thus, the electrical fields are higher than threshold value of the display medium so that modes of display medium are changed.
Reference is made to FIG. 2. FIG. 2 schematically illustrates a driving circuit for the display device in the prior art. The “ON” mode is driven by a driving common voltage 112 and a driving segment voltage 114. The “OFF” mode is driven by a driving common voltage 112 and a driving segment voltage 28. Referring to FIG. 2, a pixel with the “ON” mode and a pixel with the “OFF” mode are shown (FIG. 2 may include more pixels). The “ON” mode is indicated by a display medium active mode 24, and the “OFF” mode is indicated by a display medium inactive mode 26. However, pixels of non-display area should not be lit (even the background light should not be lit), and pixels of display area should normally be lit. If the clock signal having the waveforms as shown in FIG. 1B is applied, then a segment driving voltage VLS, ON=V(clk,−)−Vcg of the ON mode is generated. Besides, a segment driving voltage VLS,OFF=V(clk,+)−Vcg of the OFF mode is generated. The voltage V(clk,+) is the segment electrode voltage of the OFF mode, and the voltage V(clk,−) is the segment electrode voltage of the ON mode. The voltage Vcg is a common background voltage. In the prior art, the common background voltage or the segment background voltage may be floating as a result of uncertain voltage. That is, the common background or segment background may be lit or may not be lit. (It depends on the display mediums).